Role of LBD14 during ABA-mediated control of root system architecture in Arabidopsis.

The LATERAL ORGAN BOUNDARIES DOMAIN/ASYMMETRIC LEAVES2-LIKE (LBD/ASL) gene family encode plant-specific transcription factors that regulate various aspects of plant growth and development. Arabidopsis genome has 42 LBD genes. Several LBD genes, such as LBD16, -18, -29, and -33, have been shown to function in lateral root (LR) development via auxin signaling. Although abscisic acid (ABA) is a well-known antistress plant hormone regulating various plant developmental processes, it also plays a role in LR growth regulation. Our recent study showed that LBD14 expression is downregulated by ABA during the entire steps of LR development. The RNAi-induced downregulation and overexpression of LBD14 indicated that LBD14 promotes LR formation. LBD14RNAi enhanced the ABA-induced suppression of LR density compared with the wild type, suggesting that LBD14 is involved in the ABA-mediated control of LR formation. Our study provides an insight into the signaling mechanism of developmental plasticity whereby ABA controls LR branching via LBD14 downregulation under abiotic stress conditions.